14 Answers
14

Ubuntu 12.04 to 13.04

Ubuntu 12.04 Unity greeter has introduced selected user dynamic background, that means that when selecting a user from the available users list the background will change to reflect the selected user's desktop background.

By default lightdm will set /usr/share/backgrounds/warty-final-ubuntu.png as the default background and the option for the dynamic background switching on.

If you want to reset that setting to default after changing it, follow all the steps until the command above and instead use

gsettings reset com.canonical.unity-greeter draw-user-backgrounds

When you are done setting off or reseting to default the dynamic background feature you can close the terminal or type 2x exit, first to revert back to root and the second to clear the root privileges and revert back to your normal user.

Changing the default fixed background

(you will only see this one if the user did not set a desktop background picture or if the dynamic setting is set to false)

(Note: the wallpaper file cannot be located inside a encrypted user's home, those are only mounted after the user has logged in with his account.)

If you want to revert that to the default background follow all the steps until the command above but instead type

gsettings reset com.canonical.unity-greeter background

When you are done changing the default background feature or reverting back to the default one you can close the terminal or type 2x exit, first to revert back to root and the second to clear the root privileges and revert back to your normal user.

I think, adding this information will help future users like us, who want to disable any paper on lightdm. I first disabled the "drawing-user-background" feature and then sat a background which only exists in .. (no it doesn't exists). I have now a nicer login screen.
–
Anwar ShahJul 30 '12 at 14:08

I used "Changing the default fixed background" and it works, but then I don't know why, I get a message with "low-graphics mode" after reboot and lightdm doesn't start anymore. Then I found this solution to change the lightdm background.
–
BuZZ-dEESep 7 '12 at 16:17

I have two users, each with different (custom) wallpapers. I want one user to display his own wallpapaer on the login screen, but I want the other one to display the default warty-final-ubuntu one. How would I do this? Is it even possible, without an extra program, to set login backgrounds on a per-user basis other than the user's wallpaper?
–
JamesTheAwesomeDudeJan 15 '13 at 21:27

How is it possible to change the warty-final-ubuntu.png that is shown when ubiquity installer is displayed to some other images ?
–
Roshan George Jun 22 '13 at 1:30

It's much easier and more safer to make an override file as suggested in the alternative answers
–
Robert AncellMar 26 '14 at 4:39

The first time I tried this I used a file in /home and it didn't work, I just had a black background (Maybe because /home is encrypted?). Changing it to a file in /usr/share/backgrounds/<name-of_picture>.jpg worked though.
–
Tom BrossmanOct 17 '11 at 8:04

The main answer doesn't work for me, as I'm not using unity-greeter. My lightdm is configured to use lightdm-gtk-greeter.

I found a solution by looking through the lightdm source code. It queries DBus to find the BackgroundFile property for the user. You can change this by using the d-feet program (or command-line tools).

This is a workaround for 12.04 and the current version of unity-greeter (the default "theme"). For other greeters like lightdm-gtk-greeter, the usual editing of the conf file in /etc/lightdm/ works. But unity-greeter no longer looks at unity-greeter.conf, and it's unclear how to configure it.

What I did is this: I found the image that unity-greeter insists on using. For me, it was in /usr/share/backgrounds. Move/delete/rename it. Now unity-greeter will fallback to the default background which is /usr/share/backgrounds/warty-final-ubuntu.png. Move/delete/rename that. Now you need to put another image at that location with that name. And no, it doesn't have to be a png (in fact, warty-final-ubuntu.png is actually a jpg for reasons I won't go into here). I believe the replacement must be a jpg (someone correct me if I'm wrong). Be very careful here. I think if lightdm can't fallback to the default background, something horrible might happen :-/ (maybe it'll only show a colored background... anyway be careful!).

In my case, I just made a symlink from another background in that location:

sudo ln -s Bird_by_Magnus.jpg warty-final-ubuntu.png

run this command while you are in /usr/share/backgrounds/ (or adjust command accordingly). Of course, replace the jpg with whatever is available and desired.

Keep in mind that if you are going to use a background in your home, you need to make sure your home is not encrypted, as lightdm will not be able to read that file until you login. Also make sure you have the right permissions on the file. If you don't know what any of this means, stick with a wallpaper that's already in /usr/share/backgrounds/. (Random tip: you can get more wallpapers from earlier versions of Ubuntu installed properly in that directory by sudo apt-get install ubuntu-wallpapers-oneiric, replace 'oneiric' with 'natty', etc.)

This what worked for me. Via nautilus, I renamed the original /usr/share/backgrounds/warty-final-ubuntu.png image file inside , then I pasted my preferred image as the login wallpaper and renamed it to warty-final-ubuntu.png, then applied the same file properties as with the original one.

In Ubuntu 12.04 you don't need to do all those command line edits anymore. All you have to do is change your wallpaper and voilá, LightDM will use it as the background (:

Sadly it seems not fully implemented yet, since when your computer starts, you see the default Ubuntu wallpaper for some seconds before it change to your wallpaper. But since we are talking about a beta (Ubuntu 12.04 is in Beta 2 right now), it's expected.

I don't think this works unless you use Unity and change your wallpaper in Unity. In any case, what you're suggesting doesn't work if you want a different wallpaper in lightdm from what you have in your desktop environment.
–
Chan-Ho SuhApr 13 '12 at 1:35

@Chan-Ho Suh True, but since he did not specified that he was using another interface, i assume he is using Unity. About the second point, true (:
–
Julian FernandesApr 13 '12 at 5:26

This is the only way to change the wallpaper at the moment.
–
GaryApr 14 '12 at 0:47

12.04

This is my solution to those who are not able to change the login screen background.

I was having this problem when I changed the wallpaper but I was getting the default Ubuntu login background. So what I did was locate the wallpaper.jpg file in terminal and change its permissions to, say:

chmod 777 walpaper.jpg

Something which gives full access and now we can see the effect. The wallpaper I choose on desktop is also seen as the login screen background. This applies for all users.